History and exam
Key diagnostic factors
common
presence of risk factors
Key risk factors include long-standing rheumatoid arthritis (RA), age >50 years, family history of RA, and white ethnicity.
splenomegaly
joint deformities
Patients typically have a history of long-standing, severe, erosive RA. Therefore, patients may have joint deformities typical of RA such as Z thumbs, swan-neck and boutonniere deformities, evidence of joint subluxation, and ankylosis. Synovitis may be mild or inactive at the time of diagnosis of FS.[3]
Other diagnostic factors
common
rheumatoid nodules
Patients tend to have more frequent and severe extra-articular manifestations of RA, including rheumatoid nodules.
uncommon
hepatomegaly
Mild hepatomegaly may be present in up to 25% of patients but is not a requirement for diagnosis.[3]
history of vasculitis
Patients tend to have more frequent and severe extra-articular manifestations of rheumatoid arthritis such as vasculitis (e.g., mononeuritis multiplex, leg ulcers, palpable purpura, or periungual infarcts).[2]
frequent skin and respiratory tract infections
Some patients may present with infections as a result of severe neutropenia, commonly pulmonary or skin infections.
Risk factors
strong
rheumatoid arthritis (RA) >10 years
Typically, FS develops late in the course of RA, usually 10 to 20 years after RA onset.[2]
family history of RA
Strong family history of RA and robust association with HLA-DR4 antigen (present in >90% of patients) is common.[8]
age >50 years
Tends to occur in the fifth to seventh decades of life.[2]
white ethnicity
Most common in white people; rare in black people.[7] This may be because people of black ancestry have a low frequency of HLA-DR4 antigen. However, other key genetic determinants may explain the discordant prevalence of FS between these two populations.
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